Ch.2 - Atoms, Molecules & Ions

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.2 - Atoms, Molecules & Ions

Problem 113a

Chapter 2, Problem 113a

(a) The unified atomic mass unit (u) is used to represent the extremely small mass of atoms. How many grams are equivalent to 1 u?

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1. The unified atomic mass unit (u) is a standard unit of mass that quantifies mass on an atomic or molecular scale. It is defined as one twelfth (1/12th) of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state.

2. The atomic mass unit is used to express the masses of atoms and molecules. It is approximately equal to the mass of a proton or a neutron.

3. The conversion factor between atomic mass units and grams is based on the physical properties of the carbon-12 atom. By definition, 1 u is equivalent to 1/12th the mass of a carbon-12 atom.

4. The mass of a carbon-12 atom is known to be approximately 1.992647 x 10^-23 grams. Therefore, 1 u, being 1/12th of this mass, is approximately 1.660539 x 10^-24 grams.

5. So, to convert atomic mass units to grams, you can use the conversion factor 1 u = 1.660539 x 10^-24 grams.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Unified Atomic Mass Unit (u)

The unified atomic mass unit (u), also known as dalton (Da), is a standard unit of mass that quantifies mass on an atomic or molecular scale. It is defined as one twelfth of the mass of a carbon-12 atom, which is approximately 1.66 x 10^-27 kg. This unit allows chemists to express atomic and molecular masses in a more manageable way, facilitating calculations in stoichiometry and molecular biology.

Conversion of Atomic Mass Units to Grams

To convert atomic mass units (u) to grams, one must recognize that 1 u is equivalent to 1.66053906660 x 10^-24 grams. This conversion is essential for relating atomic-scale measurements to macroscopic quantities, allowing chemists to calculate the mass of substances in grams based on their molecular or atomic mass expressed in u.

Importance of Mass in Chemistry

Mass is a fundamental property in chemistry that influences reactions, stoichiometry, and the behavior of substances. Understanding how to convert between atomic mass units and grams is crucial for accurately measuring reactants and products in chemical reactions, ensuring that calculations reflect the actual quantities involved in experiments and industrial processes.

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Textbook Question

The molar mass of HCl is 36.5 g/mol, and the average mass per HCl molecule is 36.5 u. Use the fact that 1 u = 1.6605 * 102 24g to calculate Avogadro's number.

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Textbook Question

Fluorine occurs naturally as a single isotope. How many protons, neutrons, and electrons are present in deuterium fluoride (2HF)? (Deuterium is 2H.)

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Textbook Question

Match the descriptions (a)–(e) with the following terms: atomic weight, atomic mass, mass number, atomic number, molar mass.(a) The mass of a specific atom such as one atom of 13C (b) The quantity determined by the number of protons in an element.(c) The number of grams in 1 mol of an element (d) The number of protons and neutrons in an element (e) The weighted average of the isotopic masses of an element's naturally occurring isotopes

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Textbook Question

(b) The mole is a unit used to represent a very large number of atoms. How many atoms are equivalent to 1 mol of atoms?

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